“Decades of rapidly expanding space activity have shown that each launch leaves an environmental footprint, and it can take a long time to understand the impact fully. This is why it is so crucial to consider the sustainability of these programmes early on,” said Jason Jabbour, Senior Officer at the UN Environment Programme (UNEP).

Why this matters

• Space debris is rapidly increasing around Earth.
• Satellite pollution may affect the atmosphere and ozone.
• UN treaties promote responsible exploration and debris reduction.
• Protecting space helps safeguard life and ecosystems on Earth.

Although international agreements are in place to avoid contaminating outer space, an estimated 140 million pieces of debris larger than one millimetre now orbit Earth.

Most of these are too small to track but they remain capable of damaging satellites and spacecraft.

But environmental concerns extend beyond the risk of collision.

Satellite constellations

Defunct satellites eventually re-enter Earth’s atmosphere, where they release metals such as aluminium, lithium and copper. Scientists are studying whether these materials could affect atmospheric chemistry, cloud formation and the ozone layer.

Detachable rocket sections also contribute to the problem. Some remain in orbit for years before breaking apart or falling back to Earth, while others fragment into thousands of pieces. Hundreds of tonnes of spacecraft and rocket bodies are estimated to re-enter the atmosphere each year, a figure that’s expected to increase as satellite constellations grow.

Smaller mission-related objects – including bolts, lens caps and protective covers – also add to orbital congestion, while repeated collisions and explosions create microscopic particles that scientists believe are already increasing the brightness of the night sky.

Enduring risk

Although most spacecraft burn up during re-entry, larger heat-resistant components can survive the journey, posing risks to people, infrastructure and marine life.

The Moon has fascinated humanity for millennia, inspiring mythology, science and navigation while quietly shaping life on Earth through its powerful gravitational influence.

Marking International Moon Day on 20 July, the United Nations is highlighting not only the importance of Earth’s closest celestial neighbour but also the environmental challenges accompanying a new era of space exploration.

Moon’s life-giving role

From nearly 400,000 kilometres away, the Moon generates tides that oxygenate coastal waters, transport nutrients and help sustain rich marine ecosystems, including the Great Barrier Reef. Scientists say understanding the Moon also offers vital clues about the origins and evolution of the wider solar system.

Interest in lunar exploration has surged in recent years. Earlier this year, NASA’s Artemis II mission carried four astronauts on a 10-day journey around the Moon as part of plans to establish a long-term human presence on its surface during the 2030s. China, India, Japan and several private companies are also pursuing ambitious lunar programmes.

But as activity in space expands, so too does concern over its environmental consequences.

The concept of space sustainability calls for exploration and activities beyond Earth to preserve the space environment for future generations.

Protection launchpad

Building on those commitments, UN Member States have adopted guidelines to limit the creation of space debris by reducing unnecessary waste, preventing explosions, avoiding the deliberate destruction of spacecraft and safely removing retired satellites and rocket stages from orbit.

Under the 1972 UN Liability Convention, launching countries are responsible for damage caused by their space objects on Earth, including launches conducted jointly by multiple countries.

To address these emerging risks, UNEP and the UN Office for Outer Space Affairs are working together to strengthen scientific understanding of the environmental impacts of space activities and to ensure environmental protection is embedded in future space governance.

As humanity prepares for a sustained return to the Moon, the UN says safeguarding space and Earth's environment must remain central to the next chapter of exploration.